Patent GB-570877-A (GB)
Title: Improvements in and relating to methods of manufacturing electrical apparatus such as electronic communication apparatus and the like
IPC: H05K1/16
Filed: 1943-08-30
Abstract: 570,877. Wireless receiving apparatus. SARGROVE, J. A. Aug. 30, 1943, No. 14129. [Classes 40 (iii) and 40 (v)] [Also in Groups XXXV, XXXVI and XXXVII] A method of manufacturing electrical apparatus comprising interrelated components and connecting conductors applied by spraying or otherwise to an insulating panel, is characterised in that the insulating panel is given a predetermined structural form which governs the electrical characteristics of the components. Figs. I and 2 show part of a wireless circuit suitable for construction by the method according to the invention. An insulating panel a has applied to its surface conductors such as e, e<3> which serve to interconnect the circuit components which include a switch o, condensers b, resistances r<1>...r<5>, inductance i, and valve holder k. The resistances are made of colloidal graphite applied either by a printing technique or by spraying through a stencil. The conductors are preferably of copper applied by spraying or electrolytically. One method is to mould the panel having the required grooves and depressions, the whole surface of the panel being metallised. The surface is then ground to leave the metal only in the grooves and depressions. Alternatively, the conductors may be on raised ridges and deposited by a printing or electrotyping process. Connections are made to conductors on the other side of the panel by means of eyelets h or rivets, which are also used to hold in position the members of the valve holder k. Condensers are formed by a plate of metal g deposited on the surface of one side of the panel and a second plate b deposited in a depression which is moulded so as to leave a dielectric web of the desired thickness. The switch o comprises fixed contacts eyeletted to. the enlarged ends of deposited conductors and selectively engageable by a bridging conductor deposited on an insulating rotor o. The Specification describes in detail the manufacture by this method of a complete 2-valve wireless receiver requiring for its completion the addition of the valves, two electrolytic condensers and a loudspeaker. Fig. 16 shows a panel 80 carrying the input circuits of the receiver, some components being deposited on the underside. The aerial is connected to one of the terminals 86b, c or d so as to be coupled through an appropriate input condenser such as 100 to the primary 96 of an input transformer tuned by an adjustable condenser 89. This comprises an electrode deposited in a depression and separated by a sheet of mica 110 from a flexible electrode 89a, variable by a screw 115a. The transformer secondary is on the underside of the panel and is tuned by a rotary condenser 94a. Pillars 70, 109, 92p serve to make connection to a second panel 1, Fig. 10, carrying the main stages of the receiver. These include a high-frequency amplifier 65 which is resistance-capacity coupled to a valve 67 which is a detector and output valve and includes a mains rectifier. A loudspeaker 68 is mounted over an opening in the panel. Electrolytic condensers 71 are held in clips. The juxtaposed panels, Fig. 18, are inserted into the rear of a cabinet 79 so as to connect the receiving apparatus to the mains supply circuits. These include voltage-droping resistances 125, 126, 127 and associated conductors deposited on the inside of the cabinet and connected to terminals 120 which can be selectively connected to a mains supply 123 according to the mains voltage, by a movable link (not shown) on the outside of the cabinet. A main supply switch, Fig. 20c, comprises a pair of contact springs 131s mounted in compression between a raised portion 133 moulded on the cabinet and a trunnion member journalled in the cabinet and having an operating handle 129 projecting through the wall. Movement of the handle causes the springs to snap into and out of engagement with conductors 130a, 130b deposited on the cabinet. Fig. 33A shows the elements of a Colpitts oscillator arranged for band-spread tuning over a number of wave bands. An insulating rotor 177 carries for each tuning band a deposited inductance 141 connected to a present condenser 182 comprising one deposited plate and a movable metal plate. These tuned circuits are connected to metallised strips 181a which engage contacts such as a, g so that by rotating disc 177 any of the tuned circuits can be connected between anode and grid of a valve inserted in valve holder V. Band-spread tuning on each band is effected by a differential condenser Z having fixed plates connected to anode and grid and the movable plate to the cathode. A deposited grid leak condenser 185 is provided. A fivepanel assembly including a cathode-ray tube for television reception is also described (Fig. 39 not shown). Figs. 40a ... c (not shown) describe a panel on which are deposited all the elements, conductors and a valve holder for mounting a " magic-eye " tuning indicator. The condenser rotor Z, Fig. 33A, is shown in section in Fig. 34B and consists of a plastic or ceramic disc having opposed depressions m in which the metallised movable plates are deposited. The disc is mounted for rotation about its centre over the fixed deposited electrodes 184g, 187, Fig. 33A. Single condensers with only one movable plate are also described. Also one or both depressions may be filled with iron dust for use with a variable inductance (Figs. 34-36 not shown). Fixed condensers made as shown in Figs. 1 and 2 may include thin ceramic sheets or layers of lacquer, or the dielectric web may include iron dust (Figs. 26-28 not shown). Inductances comprise spirals 164, 165 deposited in grooves or on ridges on one or both sides of the panel, Fig. 30A, and the coupling of superposed spirals may be varied by means of a screw-threaded magnetic core 173, Fig. 32. Alternatively, the panel between the coils may include iron dust (Figs. 26, 27 not shown), or iron dust cores may be inserted in apertures in the panel (Figs. 37A, B not shown). A valve holder for use when only a short life is required, is shown in Fig. 41. Holes 211 for the valve pins are moulded in the panel and the connecting leads 212 are deposited so as to allow metal to enter the holes to form contacts with the valve pins. Fig. 42 shows a valve holder for an electron multiplier valve in which a ring of resistance material 213 is deposited on the panel. Subsequently the metal valve contacts 214 and conducting leads 215 are applied. Fig. 30A shows a construction of inductance-coupled band-pass filter comprising deposited inductances 164, 165, each having connected halves arranged on opposite sides of the panel. Deposited condensers 166, 168 are connected in parallel with the coils. A series input resistor 170 and a series output condenser 169 completes the network. A capacity coupled band-pass filter is also described (Fig. 29 not shown).